Definition

The Sol-Gel Transition (also known as gelation) is simply a change from a liquid state to a gel state. In the liquid state, components in the liquid move about the liquid. In the gel state, these sub-units bond together to form a network extending through the whole substance. This network gives the material an elasticity, a solid-like property.

This cartoon shows the free-floating subunits in the sol (liquid) state, and the network formed in the gel state. *From Wikimedia Commons